Embodiments of the invention relate to adaptive cruise control (ACC). More specifically, embodiments of the invention relate to controlling an ACC by determining when there is a possibility of vehicle rollback.
Some ACCs stay active until the vehicle speed is zero. ACCs that “brake down to zero speed” use wheel direction sensors to determine whether the vehicle is stopped or do not allow a reacceleration of the vehicle once a deceleration-to-stop command has been issued. The reason that the ACC systems do not allow a re-acceleration once the vehicle has stopped (or is in the process of stopping) is because the vehicle may roll backwards on an uphill start. In particular, the unknown weight of the vehicle (e.g., when pulling a trailer), may lead to an incorrect estimation of the engine torque required to make the vehicle go forward. The determination of the required torque may also be complicated by gear selection, because the gear that the transmission is in influences the amount of torque required. Gear selection can be influence by a number of factors including traction control, a “snow mode” function, and other factors in which it may be desirable to start the vehicle from a standstill at higher gears.